This invention relates in general to shift levers for effecting gear changing operations in manually operable vehicle transmissions and, in particular, to a noise and vibration damper for such a shift lever.
In most vehicles, a transmission is provided in the drive train between the engine and the driven wheels. As is well known, the transmission includes a plurality of gears which are selectively engaged to provide a plurality of speed reduction gear ratios between the input and the output of the transmission. A control member within the transmission is moved by a driver of the vehicle throughout a plurality of gear ratio positions for selecting the desired speed reduction. As a result, acceleration and deceleration of the vehicle can be achieved in a smooth and efficient manner.
In many smaller vehicles, such as automobiles, the transmission functions automatically to move the control member without any intervention by the driver of the vehicle. However, such an automatic transmission is typically not used in larger vehicles, such as trucks, because of the increased size and expense. Such vehicles are, therefore, often provided with a manually operable transmission, where the shifting of the control member is accomplished by physical movement of the control member by the vehicle driver.
In order to shift the control member between the gear ratio positions in a manual transmission, a mechanical shift lever assembly is generally provided. A lower end of the Shift lever assembly extends downwardly within the transmission into engagement with the control member. The upper end of the shift lever assembly extends upwardly into an area in which it is convenient for the vehicle driver to grasp and manipulate it. Thus, when the upper end of the shift lever assembly is moved by the vehicle driver, the lower end is also moved within the transmission. By properly moving the upper end of the shift lever assembly, the vehicle driver may position the control member of the transmission to select any one of a plurality of gear ratios for use.
When the vehicle is operated, it has been found that the transmission and other components of the drive train of the vehicle vibrate to a certain extent. In addition, vibrations are generated by the vehicle engine itself during operation. All of such vibrations can be sensed by the vehicle driver as undesirable noise. To reduce the amount of this undesirable noise, the driver compartment of the vehicle is typically lined with acoustical insulating material. Unfortunately, the shift lever assembly must extend upwardly from the transmission into the driver compartment for convenient use. As a result, the shift lever assembly transmits these vibrations into the driver compartment, thereby by defeating the acoustical insulation. Further, the undesirable vibration of the upper end of the shift lever is unaffected by the acoustical insulation.
To address this, it is known to provide the shift lever assembly with a vibration and noise dampening mechanism. Such mechanisms are designed to reduce or prevent the vibrations from the engine and transmission from being transmitting through the shift lever assembly to the driver compartment of the vehicle. A typical vibration and noise dampening mechanism includes one or more elastic damping members disposed within a cylindrical housing. A lower shift lever member has a lower end connected to the transmission and an upper end secured within the housing of the dampening mechanism. An upper shift lever member has a lower end connected to the housing of the dampening mechanism. The dampening mechanisms thereby provide a mechanical connection between the lower shift lever member and the upper shift lever member which reduces the transmission of vibrations therebetween.
Known vibration and noise dampening mechanisms, however, have not proven effective in reducing the transmission of vibrations for periods of extended use. In addition, such mechanisms have often been unduly complex and difficult to construct and assemble. Accordingly, it would be desirable to provide an improved noise and vibration damper for a shift lever assembly which effectively reduces the transmission of vibration over extended periods of use. It would also be desirable to provide an improved noise and vibration damper which is simple and inexpensive to construct and assemble.